Acetylsalicylic acid loaded poly(vinyl alcohol) hemodialysis membranes: effect of drug release on blood compatibility and permeability

Preparation, mechanical properties, fatigue and tribological behavior of double crosslinked high strength hydrogel

Polyvinyl alcohol hydrogel (PVA-H) has been widely used in clinical transplantation because of its high water content, good biocompatibility and mechanical properties. However, PVA-H have some problems, such as low elongation at break, low fatigue resistance and high friction coefficient, which hinders its application in clinic. In this paper, a novel high-performance PVA hydrogel enhanced by chemical double crosslinking (CDC) method had been synthesized. The influences of chemical crosslinking agent concentration on mechanical properties, friction properties and fatigue properties of materials were systematically investigated, in order to meet the clinical application of artificial meniscus, artificial cartilage, nucleus pulposus and so on. As a result, due to the introduction of chemical bonds, CDC hydrogels have over 600% elongation at break, modulus loss after fatigue test was reduced by 42%, average coefficient during friction was reduced to 0.048, and biocompatibility performance was excellent. The PVA hydrogel enhanced by CDC method provides a new concept for us to prepare high-performance PVA hydrogel and a promising material to replace cartilage, meniscus, nucleus pulposus and other tissues.

Antibacterial activity of combination of synthetic and biopolymer non-woven structures

BACKGROUND

Fibrous structures and synthetic polymer blends offer potential usages in making biomedical devices, textiles used in medical practices, food packaging, tissue engineering, environmental applications and biomedical arena. These products are also excellent candidates for building scaffolds to grow stem cells for implantation, to make tissue engineering grafts, to make stents to open up blood vessels caused by atherosclerosis or narrowed by blood clots, for drug delivery systems for micro- to nano-medicines, for transdermal patches, and for healing of wounds and burn care. The current study was designed to evaluate the antimicrobial activity of woven and non-woven forms of nano- and macro-scale blended polymers having biocompatible and biodegradable characteristics.

METHODS

The antimicrobial activity of non-woven fibrous structures created with the combination of synthetic and biopolymer was assessed using Gram-negative, Gram-positive bacteria, such as Staphylococcus aureus, Proteus vulgaris, Escherichia coli and Enterobacter aerogenes using pour plate method. Structural evaluation of the fabricated samples was performed by Fourier transform infrared spectroscopy.

RESULTS

Broad spectrum antibacterial activities were found from the tested materials consisting of polyvinyl alcohol (PVA) with chitosan and nylon-6 combined with chitosan and formic acid.

CONCLUSIONS

The combination of PVA with chitosan was more bactericidal or bacteriostatic than that of nylon-6 combined with chitosan and formic acid. PVA combination with chitosan appears to be a broad-spectrum antimicrobial agent.

Physicochemical characterization of partially hydrolyzed poly(vinyl acetate)-borate aqueous dispersions

The dynamic and structural properties of Highly Viscous Polymeric Dispersions (HVPDs), constituted of polyvinyl alcohol obtained from the 75% hydrolysis (75PVA) of polyvinlyl acetate (PVAc) cross-linked with borate ions, were studied as a function of the 75PVA concentration at a constant ratio between the OH groups and the borate ions (OH/B(OH)4(-)). The threshold 75PVA concentration C* necessary for the formation of the three-dimensional network was determined by flow rheology. The oscillating rheology measurements were performed in the linear viscoelastic region; the relaxation spectra calculated from the frequency sweep curves showed only one peak whose width increased upon increasing the 75PVA concentration due to the broadening of the relaxation modes. The dependence of the mean relaxation time τH upon the concentration of 75PVA followed a power law expression (τH ∼ C(x) with x = 1.9) indicating that τH referred to a sticky reptation mechanism and that water was a good solvent for 75PVA as confirmed also by small angle X-rays scattering (SAXS) investigation. The HVPDs were used for the removal of grime layers from the surface of Carlo Carrà (1881-1966) paints decorating the walls of the Palazzo di Giustizia in Milan, Italy.

A review of polyvinyl alcohol and its uses in cartilage and orthopedic applications

Polyvinyl alcohol (PVA) is a synthetic polymer derived from polyvinyl acetate through partial or full hydroxylation. PVA is commonly used in medical devices due to its low protein adsorption characteristics, biocompatibility, high water solubility, and chemical resistance. Some of the most common medical uses of PVA are in soft contact lenses, eye drops, embolization particles, tissue adhesion barriers, and as artificial cartilage and meniscus. The purpose of this review is to evaluate the available published information on PVA with respect to its safety as a medical device implant material for cartilage replacement. The review includes historical clinical use of PVA in orthopedics, and in vitro and in vivo biocompatibility studies. Finally, the safety recommendation involving the further development of PVA cryogels for cartilage replacement is addressed.

Preparation and antibacterial test of chitosan/PAA/PEGDA bi-layer composite membranes

Chitosan/poly(acrylic acid)/poly(ethylene glycol) diacrylate (PEGDA) composite membranes with a bi-layer configuration were prepared and their potential application as an antibacterial material was examined. A two-step process was adopted. A dope consisting of PEGDA, acrylic acid (AA) and a photoinitiator was cast and then UV-cured on a glass substrate to form a mechanically strong, dense membrane. Subsequently, the membrane was coated with a layer of solution composed of chitosan, AA and water. As the majority of AA diffused downwards into the supporting layer underneath, chitosan coagulated with residual AA to form a nano-layer on the top surface by means of UV irradiation. Low-voltage field-emission scanning electron microscopy was used to observe the membrane morphology and to measure the thickness of the top layer. Contact angle measurements indicated a top layer mixed with chitosan and poly(acrylic acid), which was confirmed by chemical composition analysis of X-ray photon spectroscopy. The antibacterial activities of the formed membranes were tested both with respect to a Gram-negative (Escherichia coli) and a Gram-positive (Staphylococcus aureus) bacteria.

The behavior of rat tooth germ cells on poly(vinyl alcohol)

The purpose of this study was to evaluate the behaviors of rat tooth germ (TG) cells cultured on poly(vinyl alcohol) (PVA). It was found that TG cells suspended and aggregated to form three-dimensional spheroids on PVA. Compared with traditional monolayered cells on tissue culture polystyrene, TG cell spheroids on PVA obviously increased the alkaline phosphatase activity, the degree of mineralization, and upregulated both osteopontin and dentin matrix protein 1 genes, regardless of the seeding density. Surprisingly, PVA appears to activate the alkaline phosphatase activity and mineralization effects on TG cell spheroids in the absence of a differentiation medium. Furthermore, the present study indicates that integrins may play an important role in the mineralization on TG cell spheroids by adding Arg-Gly-Asp (RGD) peptides. Therefore, the information presented here should help to clarify the role of PVA in the regulation of the mineralization, differentiation and integrin-mediation of TG cells.

Novel thromboresistant materials

The development of a clinically durable small-diameter vascular graft as well as permanently implantable biosensors and artificial organ systems that interface with blood, including the artificial heart, kidney, liver, and lung, remain limited by surface-induced thrombotic responses. Recent breakthroughs in materials science, along with a growing understanding of the molecular events that underlay thrombosis, has led to the design and clinical evaluation of a variety of biologically active coatings that inhibit components of the coagulation pathway and platelet responses by surface immobilization or controlled release of bioactive agents. This report reviews recent progress in generating synthetic thromboresistant surfaces that inhibit (1) protein and cell adsorption, (2) thrombin and fibrin formation, and (3) platelet activation and aggregation.

Blood compatibility of novel poly(γ-glutamic acid)/polyvinyl alcohol hydrogels

Sodium poly(gamma-glutamic acid) (PGA), a water-soluble and biodegradable polypeptide, was reacted with polyvinyl alcohol (PVA) to form hydrogel without any chemical treatment. The gelation occurred probably due to physical cross-linking of polymer chains by interpenetrating hydrogen bonding. From the results of thermal analysis, PGA/PVA exhibited better thermal stability than native PVA. Although the swelling ratio decreased with the increase of PGA content, however, the water resistance and retention were improved. The tensile strength of the PGA/PVA hydrogel membranes was about 15-30% lower than that of the native PVA, whereas the elongation was increased 2.0-2.6 times. The amount of protein adsorbed and platelets adhered on the PGA/PVA membranes were significantly curtailed with increasing PGA content, thereby showing improved blood compatibility. The as-fabricated hydrogels were proven to be non-cytotoxic evaluated in vitro by L-929 fibroblast incubation. Overall results demonstrate that the non-cytotoxic PGA/PVA hydrogels, due to better water resistance, mechanical properties and blood compatibility could be very promising candidates for blood-contacting medical devices.